Biology subjects

Griffin, J. S.

Publications and source records attributed to Griffin, J. S..

5 recordsLinked to original sources

bioRxiv2026

The impact of P-Element-induced hybrid dysgenesis on the male germline in Drosophila simulans

The P-element, a DNA transposon, has independently invaded two Drosophila species, accompanied by rapid evolution of suppression. In the germline, suppression is mediated primarily by maternally expressed piRNAs, a class of regulatory small RNAs associated with PIWI proteins. The offspring of females that lack P-element-specific piRNAs and males that contain P-elements suffer a syndrome of deleterious phenotypes, including sterility, genome rearrangements, gonadal atrophy, and mutations, while the offspring of the reciprocal cross are normal. These effects, collectively termed hybrid dysgenesis, have been investigated primarily in female D. melanogaster. Here, we study hybrid dysgenesis in male D. simulans. Using an attached-X chromosome stock, we generated genetically identical F1 males that differed only in maternal suppression of the P-element. Using targeted sequencing of P-element breakpoints, we show that P-element transposition is elevated in dysgenic males and confirm a preference for insertion near origins of replication. Using transcriptomics, we show that dysgenic males have elevated P-element expression and reduced splicing suppression, with patterns of gene expression suggesting the loss of mature sperm cells. Fertility assays show higher rates of male sterility but otherwise modest effects on fertility. In conjunction with the transcriptomic data, small RNA sequencing confirms that the piRNA pathway functions in testes. Our results suggest that the P-element may spread more readily through males than females, as transposition rates are similar while fertility defects are less severe in males.

genetics↗

bioRxiv2021

Rapid divergence in independent aspects of the compatibility phenotype in the Spiroplasma/Drosophila interaction.

Heritable symbionts represent important components of host biology, both as antagonistic reproductive parasites and as beneficial protective partners. An important component of heritable microbes biology is their ability to establish in new host species, a process equivalent to a host shift for an infectiously transmitted parasite or pathogen. For a host shift to occur, the symbiont must be compatible with the host: it must not cause excess pathology, must have good vertical transmission, and possess a drive phenotype that enables spread. Classically, compatibility has been considered a declining function of genetic distance between novel and ancestral host species. Here we investigate the evolutionary lability of compatibility to heritable microbes by comparing the capacity for a symbiont to establish in two novel host species equally related to the ancestral host. Compatibility of the protective Spiroplasma from D. hydei with D. simulans and D. melanogaster was tested. The Spiroplasma had contrasting compatibility in these two host species. The transinfection showed pathology and low vertical transmission in D. melanogaster but was asymptomatic and transmitted with high efficiency in D. simulans. These results were not affected by the presence/absence of Wolbachia in either of the two species. The pattern of protection was not congruent with that for pathology/transmission, with protection being weaker in the D. simulans, the host in which Spiroplasma was asymptomatic and transmitted well. Further work indicated pathological interactions occurred in D. sechellia and D. yakuba, indicating that D. simulans was unusual in being able to carry the symbiont without damage. The differing compatibility of the symbiont with these closely related host species emphasises first the rapidity with which host-symbiont compatibility evolves despite compatibility itself not being subject to direct selection, and second the independence of the different components of compatibility (pathology, transmission, protection). This requirement to fit three different independently evolving aspects of compatibility, if commonly observed, is likely to be a major feature limiting the rate of host shifts. Moving forward, the variation between sibling species pairs observed above provides an opportunity to identify the mechanisms behind variable compatibility between closely related host species, which will drive hypotheses as to the evolutionary drivers of compatibility variation.

evolutionary biology↗

bioRxiv2020

Rapid molecular evolution of Spiroplasma symbionts of Drosophila

Spiroplasma are a group of Mollicutes whose members include plant pathogens, insect pathogens, and endosymbionts of animals. Spiroplasma phenotypes have been repeatedly observed to be spontaneously lost in Drosophila cultures, and several studies have documented a high genomic turnover in Spiroplasma symbionts and plant pathogens. These observations suggest that Spiroplasma evolves quickly in comparison to other insect symbionts. Here, we systematically assess evolutionary rates and patterns of Spiroplasma poulsonii, a natural symbiont of Drosophila. We analysed genomic evolution of sHy within flies, and sMel within in vitro culture over several years. We observed that S. poulsonii substitution rates are among the highest reported for any bacteria, and around two orders of magnitude higher compared with other inherited arthropod endosymbionts. The absence of mismatch repair loci mutS and mutL is conserved across Spiroplasma and likely contributes to elevated substitution rates. Further, the closely related strains sMel and sHy (>99.5% sequence identity in shared loci) show extensive structural genomic differences, which potentially indicates a higher degree of host adaptation in sHy, a protective symbiont of Drosophila hydei. Finally, comparison across diverse Spiroplasma lineages confirms previous reports of dynamic evolution of toxins, and identifies loci similar to the male-killing toxin Spaid in several Spiroplasma lineages and other endosymbionts. Overall, our results highlight the peculiar nature of Spiroplasma genome evolution, which may explain unusual features of its evolutionary ecology.

evolutionary biology↗

bioRxiv2019

Phage steering of antibiotic-resistance evolution in the bacterial pathogen Pseudomonas aeruginosa

Antimicrobial resistance is a growing global concern and has spurred increasing efforts to find alternative therapeutics. Bacteriophage therapy has seen near constant use in eastern Europe since its discovery over a century ago. One promising approach is to use phages that not only reduce bacterial pathogen loads, but also select for phage resistance mechanisms that trade-off with antibiotic resistance - so called phage steering. Recent work has shown that phage OMKO1 can interact with efflux pumps and in so doing select for both phage resistance and antibiotic sensitivity. We tested the robustness of this approach to three different antibiotics in vitro and one in vivo. We show that in vitro OMKO1 can reduce antibiotic resistance either in the absence or the presence of antibiotics. Our in vivo experiment showed that phage increased the survival times of wax moth larvae and increased bacterial sensitivity to erythromycin, both in the absence and presence of the antibiotic. We discuss the implications of our findings for future research on this promising therapeutic approach using OMKO1.

evolutionary biology↗

bioRxiv2019

Breaking barriers: The effect of protected characteristics and their intersectionality on career transition in academics

Lay summaryIn the past decade the scientific community has been trying to tackle the historical underrepresentation of women in science and the fact that gender can constitute a barrier to career success. However, other characteristics, such as being of an ethnic minority or coming from an under-privileged background, have received less attention. In this study we find that ethnicity and socioeconomic status impact detrimentally on career progression in early career scientists, despite the fact that gender is more likely to be reported as a barrier. Our data suggest we need to widen the discussion regarding diversity and equality in science to incorporate potential barriers to career success in addition to gender.\n\nAbstractThe academic disciplines of Science Technology Engineering and Mathematics (STEM) have long suffered from a lack of diversity. While in recent years there has been some progress in addressing the underrepresentation of women in STEM subjects, other protected characteristics have received less attention. In this study, we survey early career scientists in the fields of ecology, evolutionary biology, behaviour, and related disciplines. We (i) quantitatively examine the effect of protected characteristics and their intersectionality on career transition, and (ii) provide practical suggestions, based on the qualitative responses of those surveyed, for overcoming some of the barriers we identified. We found that socioeconomic background and ethnicity impacted negatively on the quantitative measures of career progression we examined. Respondents that were female, LGBT, and from a lower socioeconomic background were more likely to report having faced a barrier, and the most frequent barrier named was related to gender. Our results suggest that respondents may have felt more confident discussing the experiences they have had related to their gender, potentially because there is now widespread discourse on this subject. However, respondents were less likely to discuss barriers they have faced in relation to ethnicity and socioeconomic status, despite the fact that the data indicates these are more detrimental to career progression. This may reflect the fact that these characteristics have received less attention, and are therefore deemed more sensitive. We hope that this study will stimulate wider discussion, and help to inform strategies to address the underrepresentation of minority groups in STEM subjects.

scientific communication and education↗